The present invention comprises an improved pressure relief valve for venting excess pressure from pressure containment structures.
Pressure can buildup in pressure containment structures such as but not limited to storage tanks, separators, heater treaters, steam generators, transportation lines, pump lines, pipelines, conduits, and the like. Human reaction times to curtail this pressure buildup may be unacceptable for several reasons, including absence of any humans in the area. Accordingly, pressure containment structure pressures can rise unacceptably, thereby rupturing the pressure containment structure and possibly damaging related equipment such as pumping equipment. In typical configurations, material in the pressure containment structures can be any gas, fluid, or combinations thereof.
Relief valves can help prevent ruptures due to pressure buildup and are typically inserted into or located within or near pressure containment structures to relieve pressure when the pressure reaches a predetermined level in the pressure containment structure. However, prior art pressure relief valves typically do not have reliable pressure setting capabilities.
The prior art includes the following patents and literature references: U.S. Pat. No. 5,282,653, issued to Karl K. LaFleur and Donald R. Wade; U.S. Pat. No. 5,348,351, issued to Karl K. LaFleur and Donald R. Wade; U.S. Pat. No. 5,152,554, issued to Karl K. LaFleur and Donald R. Wade; U.S. Pat. No. 4,167,262, issued to John C. Lemmon; U.S. Pat. No. 4,173,327, issued to William R. Williams; U.S. Pat. No. 4,190,073, issued to Jack R. Claycomb; U.S. Pat. No. 4,316,598, issued to Robert L. Maggio; U.S. Pat. No. 4,795,131, issued to Robert V. Scarano and Joseph A. Bolton; U.S. Pat. No. 4,355,784, issued to Lester L. Cain; and SPM, of Ft. Worth, Tex., makers of emergency relief valves part numbers 2A18138, 2A18192, and 2A29183.
Further, sand and other contaminants may be present in the fluid or gas in the pressure containment structure, for example from the purposeful addition of sand to fluids to aid in xe2x80x9cfracturingxe2x80x9d processes oftentimes used to enhance hydrocarbon production. Typically, prior art pressure relief valves utilize a plunger with a cone-shaped head that seals against an elastomer seat. When the plunger is activated, it moves away from the seat. Pressure is reduced, and when the plunger attempts to move back against the seat, sand or other contaminants may get trapped between the plunger and the seat, preventing the pressure relief valve from resealing. This tends to limit and even disable the pressure relief valve.
Pressure relief valves in the prior art typically have limited flow rates, making them unacceptable or ill-suited for handling the amount of pressurized fluid or gas when the pressure exceeds a predetermined level.
Moreover, pressure relief valves are oftentimes difficult to redress and maintain under field conditions and accordingly are usually repaired, if at all, at a location distant from the field such as the manufacturer""s site or a repair depot.
It is therefore an objective of the present invention to provide an improved pressure relief valve with reliable pressure setting capabilities.
It is a further objective of the present invention to provide an improved pressure relief valve that prevents sand or other contaminants from getting trapped within the improved pressure relief valve.
It is a further objective of the present invention to provide an improved pressure relief valve that allows redressing and maintenance under field conditions.
The objects of the invention are achieved, generally, by a new and improved pressure relief valve, comprising a main valve body having a cylindrical cavity therein; a piston slidingly and sealing engaged within said cavity; a fluid inlet passageway in fluid communication with said piston; a fluid outlet passageway in fluid communication with said piston, said fluid inlet and fluid outlet passageways having no fluid communication with said cavity; and a regulating gas against which said piston moves in said cavity, said regulating gas having a pressure of a first predetermined value wherein said movement of said piston selectively permits fluid communication between said fluid inlet passageway and said fluid outlet passageway when pressure of fluid in said fluid inlet passageway exceeds a second predetermined value.
In another aspect of the invention, the pressure relief valve comprises a valve body having a cylindrical cavity therein having an internal sidewall of a given diameter; a piston having a cylindrical piston head with a top surface of a given area slidably positioned within said cylindrical cavity and sized to reciprocate within said cylindrical cavity while being in sealing engagement with the said sidewall, said piston also having a tubular piston stem with a sidewall and having a first open end and a second closed end in juxtaposition to said piston head, said closed end defining a face having an area smaller than said given area, said tubular piston stem having a least one port through its side wall; a fluid inlet passageway in communication with the open end of said tubular piston stem for receiving the fluid whose pressure is to be relieved when excessive; a pack off assembly within said valve body sealingly and slidably engaged against the exterior surface of the sidewall of said tubular piston stem; an end cap threadedly engaged to, and completing the closure of said valve body, said pack off assembly being in juxtaposition to said end cap; a connection to said valve body in fluid communication with said cylindrical cavity through which a pressurized gas can be used as a force against the top surface of said piston head; and a fluid outlet passageway in said valve body which is in fluid communication with the interior of said tubular piston stem through its at least one port responsive to the pressure of the fluid in said fluid inlet passageway, exceeding a predetermined pressure working against said defined face at the closed end of said tubular piston stem.